These cooling devices can be used for a plurality of applications and are readily available in a wide variety of different embodiments on the market. Thus, for example, DE 100 09 864 A1 shows a cooling device with a cooling unit as a heat exchanger through which a fluid to be cooled, especially hydraulic fluid, flows, and with a filter unit as a filter for filtering of the fluid. The filter unit together with the cooling unit are located in a common device housing. Compared to the other known fluid cooling devices, this arrangement avoids the multi-piece structure, so that the described solution can be much more compact and light, while delivering the same performance. Moreover, the conventional tubing can be omitted due to the integration of the cooling unit and filter unit in a device housing, and error sources are precluded in this way.
In the known solution the cooling unit is preferably designed as a plate-shaped finned radiator. This plate configuration is advantageous especially for installation spaces that are kept flat. Due to the alternate arrangement of the filter unit in the left or right water box of the cooling unit, the sequence of the cooling unit and filter unit can be interchanged, allowing extensive adaptation of the cooling device to the installation conditions on site. The device housing is either assembled from sheet metal parts, but configuration as a casting, especially as an aluminum diecasting, is preferable. In spite of the compact construction, the known solution is heavy, and the structural design is relatively complicated increasing production costs.
Furthermore, DE 103 28 177 A1 discloses a fluid cooling device as a modular unit with a drive motor that drives a fan impeller that can turn in the fan housing. At least one fluid pump delivers at least one fluid from a storage tank to a hydraulic working circuit with a consumer that in principle heats the fluid in operation, and leads to an assigned heat exchanger from which cooled fluid returns to the storage tank. Parts of the storage tank comprise at least in part the fan impeller and form the fan housing made preferably of a plastic material in a lightweight construction.
In spite of their compact construction, the known solutions have good cooling and filtration results for the fluid. They can reach their limits, however, where the consumer is part of an open fluid circuit, for example, where it is designed in the form of working hydraulics or as a closed, hydrostatic drive, for example, in the form of a traveling mechanism. In these applications, problem-free operation of the consumer can be ensured where a feed pump connected upstream of the consumer also receives the full amount of fluid required by it for the consumer.
In the other known systems, such as are used especially in vehicle engineering (construction machinery) and in which to some extent the components of the fluid cooling device, such as the heat exchanger means, filter means, etc., are spatially separated from one another and can be located at widely spaced-apart locations on the vehicle, especially in replenishment processes of the feed pump, a high replenishment pressure must be made available to ensure supply of the consumer as a result of the associated long supply distances. This arrangement has the disadvantage that the gas (air) bound in the fluid and comprising in part 10% or more of the fluid volume escapes unintentionally as a result of the high replenishment pressure. This situation then leads to a “soft” fluid or oil column, and adversely affects the uniform supply of the feed pump with fluid. In turn, this “soft” fluid can lead to serious problems at the hydraulic consumer. In addition, this effect also leads to cavitation phenomena causing damage to the material, at least in the feed pump.